{"gene":"ABHD17B","run_date":"2026-04-28T17:12:37","timeline":{"discoveries":[{"year":2015,"finding":"ABHD17 proteins (including ABHD17B) are novel protein depalmitoylases that catalyze palmitate removal from N-Ras and PSD95; ABHD17 catalytic activity is required for N-Ras depalmitoylation and re-localization to internal cellular membranes, distinct from APT1/APT2 which act on Huntingtin but not N-Ras or PSD95.","method":"Dual pulse-chase palmitate/protein half-life assay, activity profiling (serine hydrolase activity probes), knockdown, inhibition with Palmostatin B, subcellular localization imaging","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (pulse-chase, activity profiling, KD, small-molecule inhibition, imaging), foundational paper with 273 citations","pmids":["26701913"],"is_preprint":false},{"year":2025,"finding":"ABHD17B (along with ABHD17A and ABHD17C) acts as the acyl protein thioesterase responsible for deacylation of NOD2, displacing it from the plasma membrane and endosomes; inhibiting ABHD17 increased plasma membrane localization of NOD2, enhanced NF-κB activation, and increased pro-inflammatory cytokine production.","method":"RNA interference, small-molecule inhibitors, confocal microscopy, acyl-resin-assisted capture (acyl-RAC), immunoblotting, cytokine multiplex assays in engineered cell lines","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (RNAi, chemical inhibition, acyl-RAC, imaging, functional cytokine readout), replicated as preprint and peer-reviewed publication","pmids":["40054525","38187608"],"is_preprint":false},{"year":2022,"finding":"ABHD17B acts as a depalmitoylase for hexokinase 1 (HK1) in hepatic stellate cells; nuclear receptor Nur77 transcriptionally activates ABHD17B expression to inhibit HK1 palmitoylation, consequently attenuating HK1 secretion via large extracellular vesicles; TGF-β-activated Akt represses Nur77 by phosphorylation and degradation, reducing ABHD17B expression and promoting HK1 release.","method":"Palmitoylation assays, extracellular vesicle fractionation, transcriptional reporter assays, Akt inhibition/activation, co-immunoprecipitation, immunoblotting in hepatic stellate cells","journal":"Nature metabolism","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal biochemical and cellular methods in a high-impact journal with 103 citations; identifies ABHD17B as a Nur77 transcriptional target and functional depalmitoylase of HK1","pmids":["36192599"],"is_preprint":false},{"year":2025,"finding":"ABHD17B promotes hepatic stellate cell (HSC) fibrotic activity through pathways independent of depalmitoylation, including interaction with MYO1B to modulate gene expression and HSC migration; depletion of ABHD17B reduces COL1A1 and ACTA2 expression, promotes lipid droplet accumulation, and protects mice from liver fibrosis in vivo.","method":"High-throughput siRNA screen in primary human HSC myofibroblasts, co-immunoprecipitation/interaction studies with MYO1B, gene expression assays, lipid droplet imaging, in vivo mouse liver injury model","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA screen plus in vivo validation and co-IP with MYO1B, but MYO1B interaction mechanistic details are limited to a single study","pmids":["40025044"],"is_preprint":false},{"year":2026,"finding":"ABHD17B functions as a depalmitoylase for ASCT2 (glutamine transporter), counteracting ZDHHC14-mediated palmitoylation of ASCT2 at Cys39 and Cys48; ABHD17B activity stabilizes ASCT2 by preventing its lysosomal degradation.","method":"Palmitoylation assays, mutagenesis of ASCT2 cysteine residues, overexpression/knockdown of ABHD17B and ZDHHC14, protein stability/degradation assays","journal":"Cell discovery","confidence":"Medium","confidence_rationale":"Tier 2 — site-specific mutagenesis plus biochemical assays, but single study","pmids":["41730846"],"is_preprint":false},{"year":2025,"finding":"The middle-region cysteine residues (C14, C15) of ABHD17A's N-terminal palmitoylation code are critical for plasma membrane targeting and catalytic activity; this requirement for the middle region is conserved in ABHD17B and ABHD17C, as shown by mutagenesis.","method":"Mutagenesis of N-terminal cysteine cluster, confocal microscopy, biochemical palmitoylation/acylation assays, alanine scanning","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 1-2 — mutagenesis with functional readout, but ABHD17B conservation noted as secondary finding in a study primarily focused on ABHD17A","pmids":["41155484"],"is_preprint":false}],"current_model":"ABHD17B is a serine hydrolase depalmitoylase (acyl protein thioesterase) that removes S-palmitoyl modifications from multiple substrates including N-Ras, PSD95, NOD2, HK1, and ASCT2, thereby regulating their membrane localization and downstream signaling; its own plasma membrane targeting requires palmitoylation of conserved N-terminal cysteines, and it can also act through depalmitoylation-independent mechanisms (e.g., interaction with MYO1B) to regulate cell migration and gene expression in hepatic stellate cells."},"narrative":{"teleology":[{"year":2015,"claim":"Identification of ABHD17 proteins as bona fide depalmitoylases for N-Ras and PSD95 resolved which thioesterases govern palmitate turnover on these substrates, distinguishing them from the previously characterized APT1/APT2 enzymes.","evidence":"Dual pulse-chase palmitate/protein half-life assays, activity-based serine hydrolase profiling, knockdown, and imaging in mammalian cells","pmids":["26701913"],"confidence":"High","gaps":["Full substrate repertoire of ABHD17B beyond N-Ras and PSD95 was unknown","Structural basis for substrate recognition not determined","Relative contributions of ABHD17A, B, and C to depalmitoylation were not deconvolved"]},{"year":2022,"claim":"Demonstrating that ABHD17B depalmitoylates HK1 in hepatic stellate cells and is transcriptionally controlled by Nur77 established a signaling axis (TGF-β → Akt → Nur77 → ABHD17B → HK1) linking metabolic signaling to extracellular vesicle-mediated HK1 secretion.","evidence":"Palmitoylation assays, extracellular vesicle fractionation, transcriptional reporters, and Akt modulation in hepatic stellate cells","pmids":["36192599"],"confidence":"High","gaps":["Whether Nur77-dependent transcriptional regulation of ABHD17B operates in cell types beyond hepatic stellate cells was not tested","Direct enzymatic kinetics of ABHD17B on HK1 not measured"]},{"year":2025,"claim":"Showing that ABHD17 family members depalmitoylate NOD2 to displace it from membranes and dampen NF-κB signaling extended the substrate scope to innate immune receptors and revealed a functional role in controlling inflammatory cytokine output.","evidence":"RNAi, chemical inhibitors, acyl-RAC, confocal microscopy, and cytokine multiplex assays in engineered cell lines","pmids":["40054525","38187608"],"confidence":"High","gaps":["Individual contribution of ABHD17B versus ABHD17A/C to NOD2 depalmitoylation not fully resolved","In vivo relevance for inflammatory bowel disease or other NOD2-linked disorders not established"]},{"year":2025,"claim":"Discovery that ABHD17B promotes hepatic stellate cell fibrotic activation partly through a depalmitoylation-independent interaction with MYO1B revealed a non-catalytic function that regulates cell migration and fibrogenic gene expression.","evidence":"High-throughput siRNA screen in primary human HSC myofibroblasts, co-IP with MYO1B, gene expression analysis, and in vivo mouse liver injury model","pmids":["40025044"],"confidence":"Medium","gaps":["MYO1B interaction validated only by co-IP in a single study; reciprocal pull-down or domain mapping not reported","Mechanism by which ABHD17B–MYO1B interaction modulates gene expression is undefined","Whether the non-catalytic role is specific to hepatic stellate cells is unknown"]},{"year":2025,"claim":"Mutagenesis of the conserved N-terminal cysteine cluster demonstrated that middle-region palmitoylation sites are essential for plasma membrane targeting and catalytic function of the ABHD17 family, clarifying how the enzyme reaches its substrates.","evidence":"Alanine scanning of N-terminal cysteines, confocal microscopy, and acylation assays; conservation in ABHD17B confirmed by mutagenesis","pmids":["41155484"],"confidence":"Medium","gaps":["ABHD17B-specific mutagenesis was secondary to ABHD17A-focused analysis","Which palmitoyltransferase(s) modify ABHD17B N-terminal cysteines is unknown"]},{"year":2026,"claim":"Identification of ASCT2 as an ABHD17B substrate showed that depalmitoylation by ABHD17B stabilizes ASCT2 protein by preventing its lysosomal degradation, linking ABHD17B to glutamine transporter homeostasis.","evidence":"Palmitoylation assays, Cys39/Cys48 mutagenesis, ABHD17B and ZDHHC14 overexpression/knockdown, protein degradation assays","pmids":["41730846"],"confidence":"Medium","gaps":["Single study; independent replication needed","Physiological consequences of ASCT2 stabilization by ABHD17B (e.g., on glutamine metabolism) not explored","Whether ABHD17A/C share this substrate specificity is untested"]},{"year":null,"claim":"No crystal or cryo-EM structure of ABHD17B has been reported, and the structural basis for its broad substrate recognition, the determinants distinguishing it from ABHD17A/C, and the mechanism of its non-catalytic MYO1B-dependent functions remain open questions.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of ABHD17B","Paralog-specific substrate selectivity among ABHD17A/B/C not systematically mapped","In vivo genetic models (knockout mice) for ABHD17B specifically have not been characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,2,4]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,4]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,5]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2,4]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,2]}],"complexes":[],"partners":["NRAS","DLG4","NOD2","HK1","ASCT2","MYO1B","ZDHHC14"],"other_free_text":[]},"mechanistic_narrative":"ABHD17B is a serine hydrolase that functions as an acyl protein thioesterase (depalmitoylase), removing S-palmitoyl modifications from diverse substrates including N-Ras, PSD95, NOD2, hexokinase 1 (HK1), and ASCT2, thereby controlling their membrane association, subcellular localization, and downstream signaling [PMID:26701913, PMID:40054525, PMID:36192599, PMID:41730846]. Its own plasma membrane targeting depends on palmitoylation of conserved N-terminal cysteine residues, with middle-region cysteines being critical for catalytic competence [PMID:41155484]. In hepatic stellate cells, ABHD17B is transcriptionally activated by the nuclear receptor Nur77 and depalmitoylates HK1 to attenuate its secretion via large extracellular vesicles; ABHD17B also promotes fibrotic gene expression and cell migration through a depalmitoylation-independent interaction with MYO1B, and its depletion protects mice from liver fibrosis [PMID:36192599, PMID:40025044]."},"prefetch_data":{"uniprot":{"accession":"Q5VST6","full_name":"Alpha/beta hydrolase domain-containing protein 17B","aliases":[],"length_aa":288,"mass_kda":32.2,"function":"Hydrolyzes fatty acids from S-acylated cysteine residues in proteins (PubMed:26701913). Has depalmitoylating activity towards DLG4/PSD95 (PubMed:26701913). Has depalmitoylating activity towards GAP43 (By similarity). Has depalmitoylating activity towards MAP6 (By similarity). Has depalmitoylating activity towards NRAS (PubMed:26701913)","subcellular_location":"Cell membrane; Recycling endosome membrane; Cell projection, dendritic spine; Postsynaptic density membrane","url":"https://www.uniprot.org/uniprotkb/Q5VST6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ABHD17B","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ABHD17B","total_profiled":1310},"omim":[{"mim_id":"617943","title":"ABHYDROLASE DOMAIN-CONTAINING PROTEIN 17B, DEPALMITOYLASE; ABHD17B","url":"https://www.omim.org/entry/617943"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ABHD17B"},"hgnc":{"alias_symbol":["CGI-67"],"prev_symbol":["C9orf77","FAM108B1"]},"alphafold":{"accession":"Q5VST6","domains":[{"cath_id":"3.40.50.1820","chopping":"32-283","consensus_level":"medium","plddt":96.3554,"start":32,"end":283}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VST6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VST6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VST6-F1-predicted_aligned_error_v6.png","plddt_mean":92.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ABHD17B","jax_strain_url":"https://www.jax.org/strain/search?query=ABHD17B"},"sequence":{"accession":"Q5VST6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5VST6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5VST6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VST6"}},"corpus_meta":[{"pmid":"26701913","id":"PMC_26701913","title":"ABHD17 proteins are novel protein depalmitoylases that regulate N-Ras palmitate turnover and subcellular localization.","date":"2015","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/26701913","citation_count":273,"is_preprint":false},{"pmid":"36192599","id":"PMC_36192599","title":"HK1 from hepatic stellate cell-derived extracellular vesicles promotes progression of hepatocellular carcinoma.","date":"2022","source":"Nature metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/36192599","citation_count":103,"is_preprint":false},{"pmid":"28630138","id":"PMC_28630138","title":"Targeting the Ras palmitoylation/depalmitoylation cycle in cancer.","date":"2017","source":"Biochemical Society transactions","url":"https://pubmed.ncbi.nlm.nih.gov/28630138","citation_count":64,"is_preprint":false},{"pmid":"34869349","id":"PMC_34869349","title":"Dynamic Expression and Regulatory Network of Circular RNA for Abdominal Preadipocytes Differentiation in Chicken (Gallus gallus).","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34869349","citation_count":22,"is_preprint":false},{"pmid":"40054525","id":"PMC_40054525","title":"Attenuating ABHD17 Isoforms Augments the S-acylation and Function of NOD2 and a Subset of Crohn's Disease-associated NOD2 Variants.","date":"2025","source":"Cellular and molecular gastroenterology and hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/40054525","citation_count":6,"is_preprint":false},{"pmid":"38187608","id":"PMC_38187608","title":"Attenuating ABHD17 isoforms augments the S-acylation and function of NOD2 and a subset of Crohn's disease-associated NOD2 variants.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38187608","citation_count":6,"is_preprint":false},{"pmid":"38389525","id":"PMC_38389525","title":"Identification of important modules and biomarkers in tuberculosis based on WGCNA.","date":"2024","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/38389525","citation_count":4,"is_preprint":false},{"pmid":"34944196","id":"PMC_34944196","title":"A Transcriptomic Analysis of Gonads from the Low-Temperature-Induced Masculinization of Takifugu rubripes.","date":"2021","source":"Animals : an open access journal from MDPI","url":"https://pubmed.ncbi.nlm.nih.gov/34944196","citation_count":4,"is_preprint":false},{"pmid":"40025044","id":"PMC_40025044","title":"Screening the human druggable genome identifies ABHD17B as an anti-fibrotic target in hepatic stellate cells.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40025044","citation_count":1,"is_preprint":false},{"pmid":"41155484","id":"PMC_41155484","title":"Palmitoylation Code and Endosomal Sorting Regulate ABHD17A Plasma Membrane Targeting and Activity.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41155484","citation_count":0,"is_preprint":false},{"pmid":"41730846","id":"PMC_41730846","title":"ASCT2 palmitoylation regulated by JNK1-ZDHHC14 axis orchestrates glutamine metabolism and NSCLC progression.","date":"2026","source":"Cell discovery","url":"https://pubmed.ncbi.nlm.nih.gov/41730846","citation_count":0,"is_preprint":false},{"pmid":"40765861","id":"PMC_40765861","title":"Deciphering the molecular signatures of tropical Areca catechu L. under cold stress: an integrated physiological and transcriptomic analysis.","date":"2025","source":"Frontiers in plant science","url":"https://pubmed.ncbi.nlm.nih.gov/40765861","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7417,"output_tokens":1733,"usd":0.024123},"stage2":{"model":"claude-opus-4-6","input_tokens":4978,"output_tokens":2176,"usd":0.118935},"total_usd":0.143058,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2015,\n      \"finding\": \"ABHD17 proteins (including ABHD17B) are novel protein depalmitoylases that catalyze palmitate removal from N-Ras and PSD95; ABHD17 catalytic activity is required for N-Ras depalmitoylation and re-localization to internal cellular membranes, distinct from APT1/APT2 which act on Huntingtin but not N-Ras or PSD95.\",\n      \"method\": \"Dual pulse-chase palmitate/protein half-life assay, activity profiling (serine hydrolase activity probes), knockdown, inhibition with Palmostatin B, subcellular localization imaging\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (pulse-chase, activity profiling, KD, small-molecule inhibition, imaging), foundational paper with 273 citations\",\n      \"pmids\": [\"26701913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ABHD17B (along with ABHD17A and ABHD17C) acts as the acyl protein thioesterase responsible for deacylation of NOD2, displacing it from the plasma membrane and endosomes; inhibiting ABHD17 increased plasma membrane localization of NOD2, enhanced NF-κB activation, and increased pro-inflammatory cytokine production.\",\n      \"method\": \"RNA interference, small-molecule inhibitors, confocal microscopy, acyl-resin-assisted capture (acyl-RAC), immunoblotting, cytokine multiplex assays in engineered cell lines\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (RNAi, chemical inhibition, acyl-RAC, imaging, functional cytokine readout), replicated as preprint and peer-reviewed publication\",\n      \"pmids\": [\"40054525\", \"38187608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ABHD17B acts as a depalmitoylase for hexokinase 1 (HK1) in hepatic stellate cells; nuclear receptor Nur77 transcriptionally activates ABHD17B expression to inhibit HK1 palmitoylation, consequently attenuating HK1 secretion via large extracellular vesicles; TGF-β-activated Akt represses Nur77 by phosphorylation and degradation, reducing ABHD17B expression and promoting HK1 release.\",\n      \"method\": \"Palmitoylation assays, extracellular vesicle fractionation, transcriptional reporter assays, Akt inhibition/activation, co-immunoprecipitation, immunoblotting in hepatic stellate cells\",\n      \"journal\": \"Nature metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical and cellular methods in a high-impact journal with 103 citations; identifies ABHD17B as a Nur77 transcriptional target and functional depalmitoylase of HK1\",\n      \"pmids\": [\"36192599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ABHD17B promotes hepatic stellate cell (HSC) fibrotic activity through pathways independent of depalmitoylation, including interaction with MYO1B to modulate gene expression and HSC migration; depletion of ABHD17B reduces COL1A1 and ACTA2 expression, promotes lipid droplet accumulation, and protects mice from liver fibrosis in vivo.\",\n      \"method\": \"High-throughput siRNA screen in primary human HSC myofibroblasts, co-immunoprecipitation/interaction studies with MYO1B, gene expression assays, lipid droplet imaging, in vivo mouse liver injury model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA screen plus in vivo validation and co-IP with MYO1B, but MYO1B interaction mechanistic details are limited to a single study\",\n      \"pmids\": [\"40025044\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"ABHD17B functions as a depalmitoylase for ASCT2 (glutamine transporter), counteracting ZDHHC14-mediated palmitoylation of ASCT2 at Cys39 and Cys48; ABHD17B activity stabilizes ASCT2 by preventing its lysosomal degradation.\",\n      \"method\": \"Palmitoylation assays, mutagenesis of ASCT2 cysteine residues, overexpression/knockdown of ABHD17B and ZDHHC14, protein stability/degradation assays\",\n      \"journal\": \"Cell discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — site-specific mutagenesis plus biochemical assays, but single study\",\n      \"pmids\": [\"41730846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The middle-region cysteine residues (C14, C15) of ABHD17A's N-terminal palmitoylation code are critical for plasma membrane targeting and catalytic activity; this requirement for the middle region is conserved in ABHD17B and ABHD17C, as shown by mutagenesis.\",\n      \"method\": \"Mutagenesis of N-terminal cysteine cluster, confocal microscopy, biochemical palmitoylation/acylation assays, alanine scanning\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis with functional readout, but ABHD17B conservation noted as secondary finding in a study primarily focused on ABHD17A\",\n      \"pmids\": [\"41155484\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ABHD17B is a serine hydrolase depalmitoylase (acyl protein thioesterase) that removes S-palmitoyl modifications from multiple substrates including N-Ras, PSD95, NOD2, HK1, and ASCT2, thereby regulating their membrane localization and downstream signaling; its own plasma membrane targeting requires palmitoylation of conserved N-terminal cysteines, and it can also act through depalmitoylation-independent mechanisms (e.g., interaction with MYO1B) to regulate cell migration and gene expression in hepatic stellate cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ABHD17B is a serine hydrolase that functions as an acyl protein thioesterase (depalmitoylase), removing S-palmitoyl modifications from diverse substrates including N-Ras, PSD95, NOD2, hexokinase 1 (HK1), and ASCT2, thereby controlling their membrane association, subcellular localization, and downstream signaling [PMID:26701913, PMID:40054525, PMID:36192599, PMID:41730846]. Its own plasma membrane targeting depends on palmitoylation of conserved N-terminal cysteine residues, with middle-region cysteines being critical for catalytic competence [PMID:41155484]. In hepatic stellate cells, ABHD17B is transcriptionally activated by the nuclear receptor Nur77 and depalmitoylates HK1 to attenuate its secretion via large extracellular vesicles; ABHD17B also promotes fibrotic gene expression and cell migration through a depalmitoylation-independent interaction with MYO1B, and its depletion protects mice from liver fibrosis [PMID:36192599, PMID:40025044].\",\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Identification of ABHD17 proteins as bona fide depalmitoylases for N-Ras and PSD95 resolved which thioesterases govern palmitate turnover on these substrates, distinguishing them from the previously characterized APT1/APT2 enzymes.\",\n      \"evidence\": \"Dual pulse-chase palmitate/protein half-life assays, activity-based serine hydrolase profiling, knockdown, and imaging in mammalian cells\",\n      \"pmids\": [\"26701913\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Full substrate repertoire of ABHD17B beyond N-Ras and PSD95 was unknown\",\n        \"Structural basis for substrate recognition not determined\",\n        \"Relative contributions of ABHD17A, B, and C to depalmitoylation were not deconvolved\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating that ABHD17B depalmitoylates HK1 in hepatic stellate cells and is transcriptionally controlled by Nur77 established a signaling axis (TGF-β → Akt → Nur77 → ABHD17B → HK1) linking metabolic signaling to extracellular vesicle-mediated HK1 secretion.\",\n      \"evidence\": \"Palmitoylation assays, extracellular vesicle fractionation, transcriptional reporters, and Akt modulation in hepatic stellate cells\",\n      \"pmids\": [\"36192599\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether Nur77-dependent transcriptional regulation of ABHD17B operates in cell types beyond hepatic stellate cells was not tested\",\n        \"Direct enzymatic kinetics of ABHD17B on HK1 not measured\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showing that ABHD17 family members depalmitoylate NOD2 to displace it from membranes and dampen NF-κB signaling extended the substrate scope to innate immune receptors and revealed a functional role in controlling inflammatory cytokine output.\",\n      \"evidence\": \"RNAi, chemical inhibitors, acyl-RAC, confocal microscopy, and cytokine multiplex assays in engineered cell lines\",\n      \"pmids\": [\"40054525\", \"38187608\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Individual contribution of ABHD17B versus ABHD17A/C to NOD2 depalmitoylation not fully resolved\",\n        \"In vivo relevance for inflammatory bowel disease or other NOD2-linked disorders not established\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery that ABHD17B promotes hepatic stellate cell fibrotic activation partly through a depalmitoylation-independent interaction with MYO1B revealed a non-catalytic function that regulates cell migration and fibrogenic gene expression.\",\n      \"evidence\": \"High-throughput siRNA screen in primary human HSC myofibroblasts, co-IP with MYO1B, gene expression analysis, and in vivo mouse liver injury model\",\n      \"pmids\": [\"40025044\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"MYO1B interaction validated only by co-IP in a single study; reciprocal pull-down or domain mapping not reported\",\n        \"Mechanism by which ABHD17B–MYO1B interaction modulates gene expression is undefined\",\n        \"Whether the non-catalytic role is specific to hepatic stellate cells is unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mutagenesis of the conserved N-terminal cysteine cluster demonstrated that middle-region palmitoylation sites are essential for plasma membrane targeting and catalytic function of the ABHD17 family, clarifying how the enzyme reaches its substrates.\",\n      \"evidence\": \"Alanine scanning of N-terminal cysteines, confocal microscopy, and acylation assays; conservation in ABHD17B confirmed by mutagenesis\",\n      \"pmids\": [\"41155484\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"ABHD17B-specific mutagenesis was secondary to ABHD17A-focused analysis\",\n        \"Which palmitoyltransferase(s) modify ABHD17B N-terminal cysteines is unknown\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identification of ASCT2 as an ABHD17B substrate showed that depalmitoylation by ABHD17B stabilizes ASCT2 protein by preventing its lysosomal degradation, linking ABHD17B to glutamine transporter homeostasis.\",\n      \"evidence\": \"Palmitoylation assays, Cys39/Cys48 mutagenesis, ABHD17B and ZDHHC14 overexpression/knockdown, protein degradation assays\",\n      \"pmids\": [\"41730846\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single study; independent replication needed\",\n        \"Physiological consequences of ASCT2 stabilization by ABHD17B (e.g., on glutamine metabolism) not explored\",\n        \"Whether ABHD17A/C share this substrate specificity is untested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"No crystal or cryo-EM structure of ABHD17B has been reported, and the structural basis for its broad substrate recognition, the determinants distinguishing it from ABHD17A/C, and the mechanism of its non-catalytic MYO1B-dependent functions remain open questions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No structural model of ABHD17B\",\n        \"Paralog-specific substrate selectivity among ABHD17A/B/C not systematically mapped\",\n        \"In vivo genetic models (knockout mice) for ABHD17B specifically have not been characterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 2, 4]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2, 4]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"NRAS\",\n      \"DLG4\",\n      \"NOD2\",\n      \"HK1\",\n      \"ASCT2\",\n      \"MYO1B\",\n      \"ZDHHC14\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}